SURVEY OF INVERTEBRATES 127 



but, instead, a continuous glow occurred, and at oxygen 

 concentrations nearing zero the luminescence ceased en- 

 tirely. That insects do not luminesce under conditions 

 of severe lack of oxygen has been known a long time 

 (Boyle, 1667; von Grotthuss, 1807; Owsiannikow, 1864; 

 de Bellesme, 1880; Kastle and McDermott, 1910). 



4. ARACHNOIDS, TARDIGRADES, CHILOPODS AND DIPLOPODS 



The only marine arachnoid that has been used for ex- 

 periments on anaerobiosis is Limulus. Newman (1906) 

 immersed 3 young specimens in oxygen-free sea water. 

 They became entirely paralyzed after 45 hours and only 

 one showed some signs of recovery when brought into 

 aerobic surroundings. The hearts of all three animals, 

 however, were still beating. This observation, and ex- 

 periments on excised hearts demonstrated that the car- 

 diac ganglion of Limulus is fairly resistant to lack of 

 oxygen, much more so, in fact, than the central ner- 

 vous system. 



No field observations have come to the author's atten- 

 tion that would indicate a predominantly anaerobic life of 

 Limulus in nature. Due to its habit of burrowing into 

 the bottom material it ought to encounter, at least oc- 

 casionally, rather difficult respiratory conditions. This, 

 coupled with the observation that its oxygen consump- 

 tion depends to a marked degree on the oxygen tension 

 (Amberson, Mayerson and Scott, 1925; Maloeuf, 1937a) 

 leads to the supposition that anaerobic processes may 

 constitute an important part of its metabolism, but fu- 

 ture investigations alone will decide whether this assump- 

 tion is correct. 



Tardigrades and their eggs have occasionally been found 

 in oxygen-free surroundings (Lauterborn, 1916; Pennak, 

 1940). On the whole, they do not seem to be very resis- 

 tant in experimentally induced anaerobic conditious 

 when they are kept moist. That moss tardigrades become 

 asphyctic when immersed in oxygen-poor or oxygen-free 



